1. Field of the Invention
The present invention relates to an electron beam apparatus which is represented by an image forming apparatus such as an image display device.
2. Related Background Art
Up to now, there have been known two types of electron-emitting devices, i.e., a thermal electron source and a cold cathode electron source. The cold cathode electron source includes a field emission type device (hereinafter referred to as FE-type device), a metal/insulating layer/metal type device (hereinafter referred to as MIM device), a surface conduction type electron-emitting device (hereinafter referred to as SCE device).
The inventors have studied a flat type image display device as an application of the electron source in which a large number of electron-emitting devices described above are arranged. In such a thin image display device using an envelope, there is the case where spacers are used as atmospheric-pressure-resistant support structures. A thickness of the envelope can be reduced by the spacers. In particular, in the case of a large size device, the spacers are effective in reducing a weight of the device and a raw material cost. In order to electrically separate a drive potential of the electron-emitting device from a high potential of an accelerating electrode, insulating members are used for the spacers.
The flat type image display devices using the spacers are disclosed in, for example, EP 869530 (Japanese Patent Application Laid-Open No. H10-334834) (Patent Document 1) and EP 725420 (Japanese Patent Application Laid-Open No. H08-315723) (Patent Document 2).
However, according to the image display device having the spacers, in which the electron-emitting devices are arranged, the following problem is caused. That is, the spacers composed of insulating members are charged and electron orbits near the spacers are affected by the charged spacers, so that a displacement of a light emission position is caused. This causes an image deterioration such as a reduction in light emission intensity or a color blur in pixels near the spacers in the case of, for example, the image display device.
A possible cause of the charge of the spacers is an electron reflected on a face plate which is a portion to be irradiated with an electron beam. With respect to the insulating spacers, it is estimated from electron orbit calculation and experimental results that the surfaces of the spacers are positively charged by secondary electron emission. Because the kinetic energy of the electron is small in the vicinity of the electron source, the orbit thereof is greatly distorted by an electric field. In the case where the electron is intended to be reached in a desirable position of a phosphor, it is necessary to prevent the charge of the spacers, in particular, near the electron source.
In order to reduce the charge of the spacers, an idea in which a high resistance film is provided on the surface of each of the spacers is described in, for example, the above-mentioned Patent Document 1.
However, even if a pitch among the electron-emitting devices is reduced to increase the resolution of the display device, sufficient effect can not be attained. In addition, there is even a case where a slight beam displacement, which was not a problem in a conventional display device, causes degradation in quality of a display image.